Pedometers which count a number of steps of a person have been in widespread use. Activity trackers which measure an amount of activity of a person are sold these days. In recent years, instruments have been proposed which record living body data, such as electrocardiogram data, an action of a person, and the like.
Some of the instruments are worn on, for example, an arm or a belt of a person to detect a motion of the person with an acceleration sensor and determine presence or absence of a predetermined motion of the person on the basis of an output value from the acceleration sensor.
Conventional pedometers and the like and the proposed instruments, however, constantly monitor an output from an acceleration sensor and perform determination processing as to whether there is a predetermined motion. There is a not-so-small possibility that an unintended motion of a user may be wrongly determined to be a predetermined motion.
Additionally, the determination processing as to whether there is a predetermined motion is performed on the basis of the output from the acceleration sensor, which increases power consumption of an instrument using an electronic circuit, such as a central processing unit (CPU).